Calculate the Angular Sum of an N-gon

Calculator for the angular sum of a polygon or n-gon, a two-dimensional closed shape with straight lines. For every shape with n vertices and straight edges, the sum of the inner angles is equal. Best known is this from the triangle with its angular sum being always 180°. For a quadrilateral, this is 360°. The average angle is the arithmetic mean of the n-gon's angles. For a regular n-gon, it is the exact size of each angle.